Introducing samples directly into electrospray ionization mass spectrometers using microscale capillary liquid chromatography.

This unit describes the design and operation of a microscale electrospray (ES) interface suitable for the on-line liquid chromatography (LC) separation and mass spectrometry (MS) analysis of mixtures of peptides and proteins. The interface utilizes an ES needle packed with reversed-phase support. Such a design has the advantage of minimizing any void volume between the end of the column and point of electrospray ionization, thus maintaining the integrity of the LC separation and maximizing sensitivity. Here, protocols are presented for construction of an integrated LC column ES needle in-house, packing the ES needle, and mounting and using the microscale ES LC/MS interface assembly. Various options for low-flow solvent delivery systems are also discussed.